The invention relates to a window of a transparent material suitable for closing an opening in a wall of a sealed container. The window comprises at least one conical surface which via sealing means cooperates with the wall of the opening to be closed.
Windows of the type to which the present invention relates are employed in the walls of high-pressure vessels and vacuum vessels, thus enabling optical measurements to be performed on material samples located in these vessels.
The known windows are, for example, made of sapphire. Sapphire, however, is not suitable for all optical measurements.
The windows generally take the form of a cylinder with accurately parallel end faces.
Sealing between the end faces and the wall of the opening is generally obtained by firmly clamping the window in place and appyling a soft metal to the sealing faces which deforms and diffuses into the sealing faces. Very stringent requirements are then imposed on the surface condition and the accuracy of shape of the sealing faces.
Another known type of window is described in "The Review of Scientific Instruments", Volume 41, No. 12, December 1970, pages 1880-1881. This known window takes the form of a cone which cooperates with an equally conical wall of the opening. Pyrophyllite is used, as sealing material, between the sealing faces. A drawback of this window is that stringent requirements have to be imposed on the surface condition and the accuracy of shape of the sealing faces.
A further disadvantage of the known window constructions is that the permissible pressure differentials are comparatively low, which leads to a requirement for fairly great window dimensions (thickness) in the direction of the pressure differential. A thick window gives rise to a high absorption of the measuring signal.
A further disadvantage of the known windows is that after disassembly the seals are no longer reusable; either new windows have to be mounted or the disassembled windows have to be reconditioned.